JPWO2015163329A1 - Diagnostic method for solar cell module, diagnostic circuit and diagnostic system for solar cell module - Google Patents

Abstract

The solar cell module diagnosis method measures the frequency characteristic including the resonance point of impedance between the two poles of the solar cell module and the frequency characteristic including the resonance point of impedance between the output cable and the frame, and the equivalent circuit of the solar cell module. An analysis step for determining the constant, and a determination step for comparing the equivalent circuit constant determined in the analysis step with the equivalent circuit constant acquired in advance to determine a change in the state of the solar cell module.

Description

  The present invention relates to a method for diagnosing the state of a solar cell module, and a diagnostic circuit and a diagnostic system for connecting to a solar cell module for use in diagnosis.

  Solar power generation is greatly expected as an alternative energy source for thermal power generation and nuclear power generation, and the production amount of solar cells in recent years has increased dramatically. As the solar cell, a crystalline solar cell that forms a solar cell using a monocrystalline or polycrystalline silicon substrate, or a thin-film solar cell that forms a solar cell by depositing a silicon thin film on a glass substrate is used. ing. The installation unit of the solar cell in the solar power generation system is a solar cell module. A plurality of the above-described solar cells are connected in series or in parallel according to the purpose to form a panel, and a frame and a terminal box as outer frames are provided to function as a solar cell module. A solar power generation system is configured by combining a large number of solar cell modules installed on a mount, power transmission cables, power conditioners, and the like. Such a system is used not only in general household power generation applications but also in large-scale solar power plants having a power generation amount of 1 MW or more.

  Solar cell modules have no mechanically operating parts, and are generally said to have a lifetime of more than 20 years. However, in reality, there have been cases where malfunctions have occurred within a few years from the start of operation due to various causes. It has been reported. The causes of the failure are deterioration of the power generation layer in the solar cell or increase in resistance due to corrosion of the electrode part, light transmittance of the sealing material filled so as to surround the solar cell to protect the solar cell There are known causes such as decrease in insulation, deterioration in insulation, increase in wiring resistance in the solar cell module, and poor grounding of a metal gantry fixing the solar cell module. Due to these problems, the output of the solar cell module is reduced, which may eventually lead to malfunction. In order to increase the reliability of the photovoltaic power generation system and further promote the spread of the photovoltaic power generation system, there is a demand for a diagnostic technique that can detect such a deterioration state of the solar cell module at an early stage.

  If some of the solar cell modules in the photovoltaic system fail, there may be a problem that affects the entire system. Therefore, periodically determine whether each solar cell module has deteriorated, It is ideal to repair or replace the solar cell module at an appropriate timing. For this purpose, a deterioration diagnosis technique or failure prediction technique for the solar cell module is required.

  At present, as a method of confirming the operating state of the solar cell module, a method of measuring the generated current or voltage and monitoring the generated power is common. However, because the amount of power generated by the solar cell module varies greatly depending on external factors such as the amount of solar radiation at the time of measurement and weather conditions, the module operates normally only by monitoring the current, voltage, or amount of power generated by the solar cell module. It is difficult to judge whether or not. That is, in the power generation amount monitoring as described above, a so-called “0” or “1” determination such as “operating” or “not operating” is possible, but the amount of solar radiation actually varies. In the installation environment, it is difficult to determine whether or not an abnormality has occurred in the solar cell module when the amount of power generation is reduced. Moreover, even when constructing a photovoltaic power generation system, it is difficult to determine locally whether there is a problem in the connection of each module when the construction is completed or whether there is a problem in the module itself.

In recent years, module diagnostic methods using high frequencies have been proposed for such situations. An AC voltage of various frequencies is applied to the solar cell module using a frequency variable signal generator, and the frequency dependence of the impedance of the solar cell module is measured from the current and voltage waveform at each frequency. From the frequency characteristic curve obtained by this measurement and the frequency response characteristic of the impedance given by the equivalent circuit model of the solar cell module, an equivalent circuit constant that is a characteristic variable unique to the measured module can be obtained. By comparing the values of these constants with the values when the panel is normal, it is possible to detect an increase in the series resistance of the electrode or wiring and detect that an excessive contact resistance has occurred. As an example of an equivalent circuit model of a solar cell module, an inductance L of a module tab wiring and an output cable, a series resistance R _s of wiring and an electrode part, a junction capacitance C _d of a power generation layer of a solar battery cell, and an insulation resistance R _sh An equivalent circuit composed of four circuit elements is used (see, for example, Patent Document 1).

Special table 2013-527613 gazette

  Generally, polymer materials such as EVA (Ethylene-Vinyl Acetate) are used as the sealant for solar cell modules. However, exposure to ultraviolet rays or moisture from the end of the module may occur due to long-term outdoor use. Intrusion causes material to age. In Patent Document 1, a diagnostic method that does not depend on sunlight is shown, but it is assumed that the impedance between the two poles of the solar cell module is measured. Therefore, although it is possible to detect the deterioration of the power generation layer of the solar battery cell and the resistance failure of the electrode or wiring part in the module, the sealing material filled between the solar battery cell and the metal frame It is difficult to detect deterioration of light transmissive or electrical insulation characteristics. In addition, when the sealing agent is EVA, it is known that acetic acid is generated by reacting with moisture that has entered the module, so that alteration of EVA causes corrosion of electrodes or wirings in the module. Therefore, there is a strong demand for a module diagnostic apparatus and diagnostic method that can detect changes in the properties of the sealant.

  The present invention has been made in view of the above, and is capable of quantitatively detecting the degree of deterioration of the sealing material in addition to the deterioration of the solar cell and the resistance failure of the electrode of the module and the wiring part. An object is to obtain a method for diagnosing a solar cell module.

  The method for diagnosing a solar cell module according to the present invention uses a frequency variable impedance measuring instrument connected to a solar cell module having a conductive frame, and the solar cell module has frequency characteristics of impedance of the solar cell module. A diagnostic method for diagnosing a solar cell module by measuring in a time zone when the cell does not generate power, the frequency characteristics including a resonance point of impedance between the two output cables of the solar cell module, and the two output cables Measuring the frequency characteristic including the resonance point of the impedance between one of the frames and the frame, determining the equivalent circuit constant of the solar cell module from the measured frequency characteristic, and the equivalent circuit constant determined in the analyzing process The change of the state of the solar cell module is determined by comparing with an equivalent circuit constant acquired in advance. It is intended to include a determination step.

  Furthermore, a diagnostic circuit for a solar cell module according to the present invention comprises a circuit means for connecting a first output terminal of a solar cell module having a conductive frame and a blocking capacitor, a blocking capacitor and a measurement terminal of an impedance measuring instrument. Circuit means for connecting, circuit means for connecting the second output terminal of the solar cell module and the first switch, circuit means for connecting the first switch and the ground of the impedance measuring instrument, an inductor for adjusting the resonance point, A resonance point adjustment circuit in which the second switch is connected in series; a circuit means for connecting the frame and one end of the resonance point adjustment circuit; and a circuit means for connecting the other end of the resonance point adjustment circuit and the ground of the impedance measuring instrument. Are provided.

  The solar cell module diagnosis system according to the present invention includes the above-described solar cell module diagnosis circuit, an impedance measuring instrument, a first switch and a second switch of the diagnosis circuit that are responsible for calculation, data storage, and system control. A control unit for controlling and communication means for transmitting impedance information of the solar cell module to the control unit and transmitting control signals of the impedance measuring instrument, the first switch, and the second switch from the control unit.

  Furthermore, the solar cell module diagnosis system of the present invention includes means for acquiring temperature information of the solar cell module and means for transmitting the acquired temperature information to the control unit.

  According to the present invention, by acquiring and monitoring the equivalent circuit constant of the solar cell module, it is possible to quantitatively detect the deterioration of the module including the characteristic deterioration of the sealing material.

Schematic configuration diagram schematically showing a diagnostic circuit used for diagnosis of the solar cell module according to the first embodiment of the present invention. The flowchart which shows an example of the procedure diagnosed using the circuit for a diagnosis of the solar cell module concerning Embodiment 1 of this invention. The figure which shows an example of the result of having measured the impedance of the solar cell module using the circuit for diagnosis of the solar cell module concerning Embodiment 1 of this invention The figure which shows an example of the result of having measured the impedance of the solar cell module using the circuit for diagnosis of the solar cell module concerning Embodiment 1 of this invention The figure which shows the equivalent circuit model of the solar cell module concerning Embodiment 1 of this invention The figure which shows the example of the intensity characteristic of the impedance of a solar cell module, and the frequency characteristic of a phase obtained with the diagnostic method of the solar cell module concerning Embodiment 1 of this invention The figure which shows the example of the intensity characteristic of the impedance of a solar cell module, and the frequency characteristic of a phase obtained with the diagnostic method of the solar cell module concerning Embodiment 1 of this invention Shows the measured by the diagnostic method of the solar cell module according to the first embodiment of the invention, an example of a change with time of R _s and C _e of an equivalent circuit constants in outdoor exposure period of the solar cell module Schematic configuration diagram schematically showing a diagnostic circuit used for diagnosis of a solar cell module according to a second embodiment of the present invention. A flowchart which shows the example of the diagnostic procedure of the solar cell module concerning Embodiment 2 of this invention. The figure which shows the example of the frequency characteristic of the intensity | strength of an impedance and phase of a solar cell module obtained with the diagnostic method of the solar cell module concerning Embodiment 2 of this invention In the diagnostic method of the solar cell module according to the second embodiment of the present invention, shows a self-inductance L _g of the inductor for resonance point adjustment as a parameter, an example of the frequency characteristic calculated impedance intensity of the solar cell module Schematic configuration diagram schematically showing a diagnostic circuit used for diagnosis of a solar cell module according to a third embodiment of the present invention. Schematic block diagram schematically showing a diagnostic system used for diagnosis of a solar cell module according to Embodiment 4 of the present invention. Schematic configuration diagram schematically showing a diagnostic circuit used for diagnosis of a solar cell module according to Embodiment 5 of the present invention. It is a figure which shows the example of the time-dependent change of the insulation resistance _Rsh of the equivalent circuit constant during the outdoor exposure period of the solar cell module measured by the diagnostic method of the solar cell module concerning Embodiment 5 of this invention. (A) is a figure which shows the diagnostic result when not performing temperature correction, FIG.16 (b) is a figure which shows the diagnostic result when temperature correction is performed This was measured by the diagnostic method of the solar cell module according to the fifth embodiment of the invention, shows the correlation between the R _sh and the module temperature T _m of a equivalent circuit constant of the solar cell module

Embodiment 1 FIG.
A diagnostic circuit and diagnostic method for a solar cell module according to the first embodiment will be described. The solar cell module to be diagnosed in the present invention is a solar cell module on which, for example, a crystalline or thin film solar cell is mounted, and the event to be diagnosed is not only a failure state of the solar cell module but also a failure. It also includes the state of deterioration in the middle stage.

<Configuration of diagnostic circuit>
FIG. 1 is a schematic configuration diagram schematically showing a diagnostic circuit for a solar cell module according to Embodiment 1. In FIG. The solar cell module 11 is a solar cell module of a type in which a conductive metal frame 12 is arranged around it, and a plurality of solar cells are connected in series or in parallel. In addition, two terminal boxes 13 a and 13 b (hereinafter collectively referred to as terminal box 13) for taking out electric power are arranged on the back surface side of the solar cell module 11, and the respective outputs provided in the terminal box 13. Output cables 14a and 14b (hereinafter, collectively referred to as output cable 14) for extracting electric power are connected to the terminals.

  In the diagnostic circuit for the solar cell module of the present invention, the output cable 14 is connected to the impedance measuring device 16 via the connection box 15 for diagnosing the solar cell module 11. Specifically, the output terminal of the terminal box 13a on the positive electrode side of the solar cell module 11 is connected to the measurement terminal of the impedance measuring device 16 through the output cable 14a, the connection box 15, and the central conductor 18 of the coaxial cable 17. As will be described later, a DC cut blocking capacitor 21 is inserted into the junction box 15 in the middle of this path.

  On the other hand, the output terminal on the negative side of the terminal box 13b of the solar cell module 11 is connected to the ground (GND) of the measurement terminal of the impedance measuring device 16 via the output cable 14b, the connection box 15, and the outer conductor 19 of the coaxial cable 17. However, this connection can also be disconnected by turning off the first switch 22a in the connection box 15 arranged in the middle. In this case, the terminal box 13 b on the negative electrode side of the solar cell module 11 is electrically insulated from the ground of the impedance measuring device 16. Here, in the coaxial cable 17, the outer conductor 19 is electrically insulated from the center conductor 18 via the dielectric 20.

  Further, the metal frame 12 of the solar cell module 11 passes through the ground wire 23, the resonance point adjusting inductor 24 provided inside the connection box 15, and the outer conductor 19 of the coaxial cable 17, and then the ground of the impedance measuring device 16. However, this connection can also be disconnected by turning off the second switch 22b in the connection box 15 arranged on the way. In this case, the metal frame 12 of the solar cell module 11 is electrically insulated from the ground of the measurement terminal of the impedance measuring device 16. The resonance point adjusting inductor 24 and the second switch 22b are directly connected to form a resonance point adjusting circuit, and the positions of the resonance point adjusting inductor 24 and the second switch 22b are interchanged. May be. The switches 22a and 22b may be manual toggle switches, or may be switching elements such as diode switches or MOSFETs (Metal-Oxide-Semiconductor Field-Effect Transistors) driven by gate signals.

  Here, the impedance measuring device 16 is a measuring device that measures impedance using a high frequency. However, since the measurement frequency can be substantially swept, the frequency characteristic of the impedance can be measured. “Substantially sweeping the measurement frequency” refers to, for example, an operation of continuously sweeping the frequency or discretely sweeping at a constant interval, thereby determining the resonance point. As such an impedance measuring instrument 16, for example, a network analyzer, an impedance analyzer, a combination analyzer, etc. are commercially available. A frequency variable high-frequency transmitter, a current sensor, a voltage sensor, an A / D converter, or an arithmetic device is used. It may be a combination.

  1 is grounded by a 3P type outlet or a ground wire, it is not always necessary to ground, but the housing of the impedance measuring instrument 16 is electrically floated. Measurements may be made at Further, the metal frame 12 of the solar cell module 11 shown in FIG. 1 is grounded via the casing of the impedance measuring instrument 16 by the ground wire 23 when the second switch 22b is turned on, The metal frame 12 may be separately grounded using a wire. The presence / absence of grounding of the casing of the impedance measuring device 16 and the metal frame 12 of the solar cell module 11 hardly affects the result of diagnosis of the solar cell module of the present invention. With the configuration described above, a diagnostic circuit for the solar cell module is configured.

  The measurement of the impedance of the solar cell module 11 is basically performed at night time when the solar cells included in the solar cell module 11 do not generate power, that is, when the solar cell module 11 is in a dark state. When light incidents incidentally on the light receiving surface, the solar cells in the solar cell module 11 generate power, and a DC voltage of, for example, about several tens of volts is generated between the terminal boxes 13a and 13b. In preparation for such a case, a blocking capacitor 21 for DC cut is inserted between the solar cell module 11 and the measurement terminal of the impedance measuring device 16 to protect the impedance measuring device 16 from the overvoltage as described above. doing. On the other hand, the high frequency signal for measurement supplied from the measurement terminal of the impedance measuring device 16 to the solar cell module 11 easily passes through the blocking capacitor 21 and propagates to the solar cell module 11 because the frequency is sufficiently high. be able to.

<Diagnosis method>
Next, a method for diagnosing the solar cell module 11 using such a diagnostic circuit will be described in detail. FIG. 2 is a flowchart showing an example of the procedure of the solar cell module diagnosis according to the first embodiment, which is roughly divided into three steps: a first analysis step, a second analysis step, and a determination step. Here, a method will be described in which a network analyzer is used as the impedance measuring device 16, the impedance of the solar cell module 11 is measured by a so-called 1-port reflection method, and the presence or absence of deterioration of the solar cell module 11 or the degree of deterioration is diagnosed. .

  When the diagnosis of the solar cell module is started, a first analysis process is first performed. The first switch 22a of the connection box 15 is turned on to electrically connect the output terminal of the negative terminal box 13b of the solar cell module 11, the outer conductor 19 of the coaxial cable 17, and the ground of the impedance measuring device 16. (S11). Next, the second switch 22b of the connection box 15 is turned off, and the metal frame 12 of the solar cell module 11 is electrically insulated from the ground of the impedance measuring device 16 (S12). With the first switch 22a turned on and the second switch 22b turned off, the impedance measuring device 16 causes the impedance of the solar cell module 11, that is, the impedance between the output cable 14a and the output cable 14b of the solar cell module 11. Are measured (S13).

In this measurement, the impedance between the output cable 14a and the output cable 14b of the solar cell module 11 in a state where the metal frame 12 of the solar cell module 11 and the ground of the impedance measuring device 16 are electrically insulated is measured. become. Finally, a circuit analysis using an equivalent circuit model that is a first equivalent circuit described later of the solar cell module 11 is performed on the obtained impedance measurement result, and among the equivalent circuit constants unique to the solar cell module 11, Four basic circuit constants C _d , R _sh , L, R _s are obtained (S14). Here, C _d is the junction capacity of the solar cells in the solar cell module 11, R _sh is the insulation resistance of the solar cells, L is the total inductance of the output cable 14 and the tab wiring in the module, and R _s is the solar cell. It is the series resistance of the tab wiring of the electrode part or module. Details of impedance measurement (S13) and equivalent circuit analysis (S14) will be described later.

  When the first analysis step is completed, the second analysis step is subsequently performed. The first switch 22a of the connection box 15 is switched off to electrically insulate the output terminal of the negative terminal box 13b of the solar cell module 11 from the outer conductor 19 of the coaxial cable 17 and the ground of the impedance measuring device 16. (S21). Next, the second switch 22b of the connection box 15 is switched on to electrically connect the metal frame 12 of the solar cell module 11 and the ground of the impedance measuring instrument 16 (S22). With the first switch 22a turned off and the second switch 22b turned on, the impedance measuring device 16 causes the impedance of the solar cell module 11, that is, between the output cable 14a of the solar cell module 11 and the metal frame 12. Impedance is measured (S23).

In this measurement, the impedance between the output cable 14a on the positive electrode side of the solar cell module 11 and the metal frame 12 is measured. The measurement results of the impedance performs circuit analysis using the equivalent circuit model which is a second equivalent circuit to be described later of the solar cell module 11, obtains a C _e is the rest of the circuit constants of the solar cell module 11 ( S24). Here, C _e is the parasitic capacitance between the wiring member and the metal frame 12 of the solar cell module 11 is proportional to the dielectric constant of the sealing agent located between the wiring member and the frame. Details of impedance measurement (S23) and equivalent circuit analysis (S24) will be described later.

In the final determination step, the five circuit constants C _d , R _sh , L, R _s , and C _e determined in the first and second analysis steps are normalized with their initial values (S31). The initial value is, for example, a value acquired in advance when the solar cell module is installed on site and diagnosis is started, and is used as a value when the solar cell module is normal. That is, normalizing the value of the circuit constant with the initial value is equivalent to comparing the value of the circuit constant with the value when the solar cell module 11 is normal. Next, the standardized value is compared with a preset threshold value to determine whether or not the solar cell module 11 needs to be repaired or replaced, and a determination of deterioration or failure is made (S32). For example, when the standard value of the insulation resistance R _sh of the solar battery cell is equal to or less than the threshold value for insulation resistance, or when the standard value of the series resistance R _s of the module is larger than the threshold value for series resistance, the solar cell module is repaired or replaced. Can be determined to be necessary. Also, the failure time of the solar cell module 11 can be predicted by looking at the rate of change between a plurality of times for the normalized values of the equivalent circuit constants C _d , R _sh , L, R _s , and C _e. it can. In this case, the predicted failure time can be notified to the user by a visual method such as message display or lamp lighting. Thus, the degree of deterioration of the solar cell module 11 can be diagnosed quantitatively.

In the impedance measurement using the network analyzer in the first and second analysis steps, a weak high-frequency signal is sent from the measurement terminal of the impedance measuring device 16 to the solar cell module 11, and the incident wave power and the solar cell module 11 The power of the reflected wave returning to the impedance measuring device 16 is measured. The impedance measuring device 16 can obtain the reflection coefficient from the amplitude ratio and phase difference between the incident wave and the reflected wave, and finally obtain the impedance Z _PV of the solar cell module 11. In this measurement, the frequency F of the high-frequency signal is swept in a range of F ₁ <F <F ₂ with F ₁ as the lower limit and F ₂ as the upper limit, and the impedance Z _PV of the solar cell module 11 depends on the frequency F. Get sex.

In the first analysis step, the first switch 22a of the junction box 15 is turned on, the second switch 22b is turned off, and the metal frame 12 of the solar cell module 11 and the ground of the measurement terminal of the impedance measuring device 16 are insulated. An example of the result of measuring the impedance Z _PV of the solar cell module 11 in the state described above will be described. 3A shows the dependence of the intensity of the impedance Z _PV between the output cables 14 of the solar cell module 11 on the frequency F, and FIG. 3B shows the dependence of the phase of the impedance Z _{PV on} the frequency F. Represents. FIG. 3 shows that this measurement is performed, for example, at night when the solar cell module 11 is in a dark state where no power is generated. For example, the lower limit frequency is set to F ₁ = 1 kHz, the upper limit frequency is set to F ₂ = 4.8 MHz, and the frequency F It is the result of measuring the impedance Z _PV of the solar cell module 11 while increasing the value from F ₁ to F ₂ . In addition, the solar cell module used the module of the external dimensions 120cm x 100cm using the thin film cell.

When the frequency is gradually increased from F = 1 kHz, the intensity of the impedance Z _PV of the solar cell module 11 shown in FIG. 3A first decreases, and after the frequency shows the minimum value at F = 0.69 MHz, It is increasing again. On the other hand, the phase of the impedance Z _PV shown in FIG. 3B shows that the frequency is in the vicinity of F = 0.69 MHz, which is a capacitive load, from −90 ° to +90 which indicates an inductive load. It changes abruptly to ° and shows a substantially flat characteristic at F> 1 MHz.

As shown in FIG. 3, the frequency dependence of the impedance Z _PV between the output cables 14 of the solar cell module 11 measured in the first analysis step shows typical series resonance characteristics, and the intensity of Z _PV is the minimum. Thus, when the frequency at the resonance point where the phase becomes 0 °, that is, the resonance frequency F _res is obtained, F _res = 0.69 MHz. Moreover, the minimum value of the impedance was Z _PV = 1.37Ω (@ 0.69 MHz).

Next, in the second analysis step, an example of a result of measuring the impedance Z _PV of the solar cell module 11 in a state where the first switch 22a of the junction box 15 is turned off and the second switch 22b is turned on is shown. . 4A shows the dependence of the intensity of the impedance Z _PV between the output cable 14a on the positive electrode side of the solar cell module 11 and the metal frame 12 on the frequency F, and FIG. 4B shows the impedance Z _PV. The dependence of the phase on the frequency F is shown. In FIG. 4, this measurement is performed, for example, at night when the solar cell module 11 does not generate power. For example, the lower limit frequency is set to F ₁ = 1 kHz, the upper limit frequency is set to F ₂ = 4.8 MHz, and the frequency F is set to F _1. while increased to F ₂ from the results of measuring the impedance Z _PV solar cell module 11.

As shown in FIG. 4, the frequency dependence of the impedance Z _PV between the output cable 14a on the positive electrode side of the solar cell module 11 and the metal frame 12 measured in the second analysis step is the same as that in the first analysis step. Similar to FIG. 3 showing the results, the series resonance characteristics are shown, and when the resonance frequency F _res is obtained, F _res = 3.08 MHz. The minimum impedance was Z _PV = 4.86Ω (@ 3.08 MHz).

  Since these resonance frequency and minimum impedance values are determined by the state of the solar cell module, the state (for example, the degree of deterioration) of the solar cell module is constantly grasped and managed by measuring and monitoring these values. can do.

  However, even if numerical values such as the resonance frequency and the minimum value of impedance change, it is not directly known in which part of the solar cell module the problem has occurred. In order to identify the defective part, the solar cell module may be replaced with an equivalent circuit. If the value of a specific element such as a series resistance in the equivalent circuit changes, it can be considered that a defect has occurred in a part such as an electrode or a wiring portion corresponding to this element. Thus, the state of the solar cell module can be diagnosed by grasping and managing the equivalent circuit constant specific to the solar cell module.

FIG. 5 shows an equivalent circuit model in the dark state of the solar cell module 11 shown in FIG. The output cable 14 of the solar cell module 11, since its length is relatively short, the resistance component is negligible, expressed only in the inductor scan L _c of the cable. On the other hand, the main body of the solar cell module 11 uses the internal tab wiring and the series resistance R _s and parasitic inductance L _{s of} the electrode part, and further, the junction capacitance C _d and the insulation resistance R _sh of the power generation layer of the solar cell. 5 can be represented by a series-parallel circuit as shown in FIG. A state where the second switch 22b of the connection box 15 is off constitutes a first equivalent circuit.

When the second switch 22b of the connection box 15 is turned on, that is, when the metal frame 12 and the ground of the measurement terminal of the impedance measuring device 16 are connected, a second equivalent circuit is configured. Since the distance between the tab wiring arranged on the outer edge of the solar cell module 11 and the metal frame 12 is relatively short, about several mm, the parasitic capacitance C between the tab wiring and the metal frame 12 is added to the equivalent circuit of FIG. _e , it is also necessary to consider a series circuit comprising a series resistance R _g of the ground wire 23 connecting the metal frame 12 and the connection box 15 and an inductance L _g of the inductor 24 for adjusting the resonance point. Conversely, turning off the second switch 22b of the junction box 15, in the case of insulating the ground of the measuring terminals of the metal frame 12 and the impedance measuring device 16, a circuit portion including the parasitic capacitance C _e is Can be ignored.

Between the tab wires and the metal frame 12 of the solar cell module, generally EVA (Ethylene-Vinyl Acetate) sealant made of a resin such as is filled, the parasitic capacitance C _e of the wiring member sealing since it depends on the dielectric constant of the sealing agent, if constantly monitors the value of C _e of the solar cell module is considered that it becomes possible to quantitatively grasp a degree of degradation and alteration of the sealant.

The impedance Z _PV of the solar cell module 11 measured in the first analysis step is that the first switch 22a and the second switch 22b of the connection box 15 are turned on and the second switch 22b is turned off. The capacity C _e can be ignored and is considered to be expressed by the following formula (1).

Here, ω is an angular frequency (F = ω / (2π)), L is the total inductance L (= L _c + L _s ) of the inductance L _c of the output cable 14 and the inductance L _{s of the} module body, and j is a complex number. , And the values of ω and circuit constants C _d , R _sh , and L are

の関係を満たすときに、Ｚ_ＰＶの虚部の値はゼロになり、このときＺ_ＰＶの強度は最小、位相は０°になる。すなわち、これが太陽電池モジュール１１の等価回路の共振条件であり、Ｃ_ｄ、Ｒ_ｓｈ、Ｌの値が与えられているときには、共振周波数Ｆ_ｒｅｓは次の数式（３）により得られる。

When satisfying the relationship, the value of the imaginary part of Z _PV is zero, the intensity of the time Z _PV minimum phase becomes 0 °. That is, this is the resonance condition of the equivalent circuit of the solar cell module 11, and when the values of C _d , R _sh , and L are given, the resonance frequency F _res can be obtained by the following equation (3).

When the frequency range is appropriately selected, the impedance Z _PV of the solar cell module 11 exhibits, for example, the resonance characteristics as shown in FIG. 3, and the intensity of Z _PV greatly changes in the frequency region before and after the resonance frequency _Fres . In this region, it is desirable to fit the mathematical formulas (1) and (3) to the actually measured values. By the fitting operation, the four circuit constants C _d , R _sh , L, and R _s that are the fitting parameters in the equations (1) and (3) can be obtained relatively easily.

It is not always necessary to use such resonance characteristics when fitting Equation (1), but it is best to perform fitting in the frequency region before and after the resonance frequency _Fres in order to improve fitting accuracy. Become.

As a specific example, FIG. 6 shows the result of fitting in the frequency region from F = 0.1 MHz to 1.3 MHz as a region including the resonance frequency F _res (= 0.69 MHz) in FIG. Here, FIG. 6A shows the dependency of the intensity of the impedance Z _PV on the frequency F, and FIG. 6B shows the dependency of the phase of the impedance Z _PV on the frequency F. Also, the circled plots in the figure are measured values of impedance, and the solid line is the result of fitting equation (1). It can be seen that the measured values and the fitting results are in good agreement with the intensity and phase of the impedance. The values of equivalent circuit constants obtained by this fitting are as follows: junction capacitance C _d = 25.4 nF, insulation resistance R _sh = 12.1 kΩ, total inductance L (= L _c + L _s ) = 2.1 μH, series resistance R _s = 1.5Ω. Thus, in the first analysis step, C _d , R _sh , L, and R _s that are four basic parameters of the solar cell module are output.

Next, in the second analysis step, since the first switch 22a of the junction box 15 is turned off and the second switch 22b is turned on, the output cable 14a on the positive electrode side of the solar cell module 11 and the metal frame 12 are turned on. The impedance Z _PV between the two is measured. As described above, the equivalent circuit in this case connects the inductance L _c of the output cable 14 a, the parasitic capacitance C _e between the tab wiring in the module and the metal frame 12, and the metal frame 12 and the connection box 15. A series circuit comprising a series resistance R _g of the ground wire 23 and an inductance L _{g of the} resonance point adjusting inductor 24. Therefore, it is considered that the impedance Z _PV measured in the second analysis step can be expressed by the following formula (4).

Here, when the values of each frequency ω and circuit constants L _c , L _g , and C _e satisfy the relationship ω (L _c + L _g ) −1 / ωC _e = 0, the value of the imaginary part of Z _PV is zero, the intensity of the time Z _PV minimum phase becomes 0 °. Therefore, the resonance frequency F _res is obtained by the following formula (5).

When the frequency range is appropriately selected, the impedance Z _PV of the solar cell module 11 exhibits, for example, resonance characteristics as shown in FIG. 4, and the intensity of Z _PV greatly changes in the frequency region before and after the resonance frequency F _res . In this region, the mathematical formulas (4) and (5) may be fitted to the actually measured values. Accordingly, the three circuit constants C _e , (L _c + L _g ), and R _g that are fitting parameters in the equations (4) and (5) can be obtained relatively easily.

As a specific example, the result of fitting in the frequency region from F = 2 MHz to 4 MHz as a region including the resonance frequency F _res (= 3.08 MHz) in FIG. 4 will be described. Here, FIG. 7A shows the dependence of the intensity of the impedance Z _PV on the frequency F, and FIG. 7B shows the dependence of the phase of the impedance Z _PV on the frequency F. Also, the circled plots in the figure are measured values of impedance, and the solid line is the result of fitting equation (4). As in the case of the first analysis step shown in FIG. 6, it can be seen that in this second analysis step, the measured values and the fitting results are in good agreement. The values of the equivalent circuit constants obtained by this fitting are the capacitance C _e = 661 pF between the tab wiring and the frame, the total inductance (L _c + L _g ) = 4.0 μH, and the series resistance R _g = 4. It was 9Ω. Here, specific circuit constants to the solar cell module to be measured is only C _e, other parameters _(L c ₊ L _g), since R _g is determined by the measurement system, in the second analysis step only the C _e Is output.

As described above, when the impedance Z _PV is measured in the second analysis step, if the L _g of the resonance point adjusting inductor 24 is changed, the resonance frequency F _res changes according to the equation (5). If there is a range limit may be the peak of the resonance by choosing the value of this L _g properly observes within the measurement frequency. However, since a problem appears in signal transmission if the frequency to be measured is too high, the measurement frequency should be 10 MHz or less, preferably 5 MHz or less, more preferably 3 MHz or less. In the solar cell module using the above example, the capacitance between the wiring member and the frame are C _{e =} 661pF, so further parasitic inductance of the output cable may be estimated as L _c ~0.8μH, the L _g If the value is about 3 μH or more, the resonance frequency F _res can be suppressed to 3 MHz or less. In addition, the output when the inductance L _c of cable 14 is sufficiently large, or if the parasitic inductance of the grounding wire 23 is sufficiently large, even if there is no inductor 24 for resonance point adjustment can occur series resonance. In any case, since the strength of the impedance Z _PV greatly changes in the frequency region before and after the resonance frequency F _res , the equations (4) and (5) are fitted to the actually measured values in this region to obtain the characteristics of the sealant. it can be determined with high values of the corresponding C _e accuracy.

  In the first embodiment, the measurement terminal of the impedance measuring device 16 is connected to the positive terminal box 13a of the solar cell module 11, and the ground of the measurement terminal of the impedance measuring device 16 is connected to the negative terminal box 13b. Although the measurement method is illustrated, conversely, the measurement terminal of the impedance measuring device 16 is connected to the terminal box 13b on the negative electrode side of the solar cell module 11, and the ground of the measurement terminal of the impedance measuring device 16 is connected to the terminal box 13a on the positive electrode side. May be connected, and similar results and effects are obtained.

  Next, a result of diagnosing the solar cell module using the circuit for diagnosing the solar cell module and the diagnostic method shown in the first embodiment will be described. Here, one solar cell module is installed outdoors, and the result of evaluating the change in the state of this module will be described as an example.

Diagnostic procedures of the solar cell module, in accordance with the flowchart of FIG. 2, _C d is a first analysis _step, R sh, L, and _{R s,} obtains a _{C e} in the second analysis step, and records these. Moreover, in the impedance measurement of the solar cell module, the measurement was performed at night using the diagnostic circuit shown in FIG. Note that a network analyzer was used as the impedance measuring device 16. From the obtained impedance measurement results, the equivalent circuit constants C _d , R _sh , L, R _s , and C _e of the solar cell module were obtained by the equivalent circuit analysis method described in FIGS. 6 and 7. Outdoor exposure assessment was performed over 168 days, during which the variation in equivalent circuit constants was recorded.

8 was measured by the diagnostic method of the solar cell module according to the first embodiment, is a diagram showing an example of a change with time of R _s and C _e of an equivalent circuit constants in outdoor exposure period of the solar cell module. Of equivalent circuit constants of the solar cell module, in FIG. 8 (a) the time course of the series resistance R _s of the solar cell module as an example, the change of capacitance with time C _e between the wiring member and the metal frame 12 Figure 8 This is shown in (b). Here, the value of R _s and C _e is the initial value before weathering and standardized, these initial values are used as a value when the solar cell module is normal. That, R _s and C _e in the figure, each of the initial value, that is, the solar cell module 11 is normalized by the value at normal, when each value solar cell module 11 is normal It corresponds to the result of comparison with the value and is a value that quantitatively indicates the degree of deterioration.

As shown in FIG. 8 (a), in the outdoor exposure of 168 days, the series resistance R _s is hardly changed. However, with respect to the capacitance C _e between the wiring member and the metal frame 12 of FIG. 8 (b), the value of C _e if exposure days exceeds approximately 80 days gradually decreases, and the initial value after 168 days Compared to about 15%. Further, although not shown here, other circuit constants C _d , R _sh , and L of the solar cell module were not clearly changed as in the case of R _{s in} FIG. Thus, in the comparatively short-term exposure test of 168 days, the characteristics of the solar cell and the resistance of the module wiring or the electrode part have hardly changed, but the sealing agent used for sealing the module As a result, a slight change was observed as early as possible.

Since the decrease of the capacitance C _e between the wiring member and the frame corresponding to the decrease in the dielectric constant of the sealant, the water entering from the ultraviolet or module end receives while installed outdoors, the molecules of the sealing material It is thought that some change in the structure occurred, resulting in a change in material properties. If such a change further progresses, it is considered that the light transmittance or moisture barrier property of the sealant deteriorates, and the power generation characteristics of the solar cell module also appear. It is also known that acetic acid or the like is generated in the module due to the alteration of the sealant, and as a result, the output of the module is reduced due to corrosion of the wiring or the electrode.

Diagnostic circuitry and diagnostic methods of the conventional solar cell module (for example, see Patent Document 1), it is possible to obtain a capacity C _e between the wiring member and the metal frame 12 corresponding to the sealant of the solar cell module However, in the diagnostic circuit and the diagnostic method of the first embodiment, the state of the sealing material can be detected in addition to the deterioration of the solar battery cell and the resistance failure of the module electrode or wiring part. Can be comprehensively diagnosed. Accordingly, it is possible to prompt the user to repair or replace the solar cell module at an appropriate timing before the failure occurs, and it becomes possible to repair or replace the solar cell module before the serious failure occurs. It has the effect that maintenance of the whole solar cell system including a plurality of can be performed efficiently.

Further, by providing the first switch 22a and second switch 22b of the junction box 15, taking a large self-inductance _{L g,} by increasing the total inductance L, reduce the resonance frequency to about 100kHz~2MHz It becomes possible. By using such a relatively low frequency resonance, it is not necessary to use a measuring device having excellent frequency characteristics exceeding 2 MHz, and the cost of the diagnostic circuit can be reduced. Further, by providing the first switch 22a and second switch 22b, since the equivalent circuit to be analyzed is simplified, the value of the junction capacitance C _d is increasing the accuracy of the calculations can be determined accurately.

Embodiment 2. FIG.
Next, a diagnostic circuit and a diagnostic method for a solar cell module according to the second embodiment will be described. Below, it demonstrates focusing on a different part from Embodiment 1. FIG.

  In the first embodiment, as shown in the flowchart of FIG. 2, the first switch 22a and the second switch 22b of the junction box 15 in FIG. 1 are switched, and the impedance measurement of the solar cell module 11 is performed twice in total. ing. For this reason, in the outdoor outdoor environment where the solar cell module 11 and the junction box 15 are installed, a contact failure occurs in the first switch 22a or the second switch 22b due to long-term use, or the switch breaks down. In addition, there is a possibility that the diagnostic circuit of the solar cell module 11 may fail due to a failure of the switch control device.

  FIG. 9 is a schematic configuration diagram schematically showing a diagnostic circuit of the solar cell module according to the second embodiment. Compared with FIG. 1, the inside of the connection box 15 is different in that it is directly connected without a switch, and the output terminal of the negative terminal box 13b and the ground of the measurement terminal of the impedance measuring device 16 are different. Electrically connected. Further, the metal frame 12 and the ground of the measurement terminal of the impedance measuring device 16 are also connected. This is the same state as when both the first switch 22a and the second switch 22b in FIG. 1 are fixed on. FIG. 10 is a flowchart of an example of a diagnostic procedure for the solar cell module according to the second embodiment. In the diagnosis, the impedance measurement (S113) of the solar cell module 11 which is an analysis step is performed, and then the equivalent circuit analysis (S114) is performed. Next, circuit constant normalization (S131) and deterioration or failure determination (S132), which are determination steps, are performed.

  In this way, the wiring of the junction box 15 is directly connected without a switch, and impedance measurement is performed in the same state as when both the first switch 22a and the second switch 22b in FIG. 1 are fixed on. As a result, deterioration or failure of these switches does not occur, and the long-term reliability of the diagnostic apparatus is significantly improved.

In the second embodiment, when impedance measurement and equivalent circuit analysis of the solar cell module 11 are performed, as shown in the equivalent circuit of FIG. 5, the solar cell is the inductance L _c of the output cable 14 and the impedance of the module body. In addition to the cell junction capacitance C _d and insulation resistance R _sh , wiring inductance L _s , electrode and wiring section series resistance R _s , capacitance C _e between the tab wiring in the module and the metal frame 12, metal frame It is also necessary to consider simultaneously the impedance of the branch circuit composed of the series resistance R _g of the ground wire 23 connecting the connection box 12 and the connection box 15 and the self-inductance L _{g of} the resonance point adjusting inductor 24.

FIG. 11 is a diagram illustrating an example of the result of measuring the impedance Z _PV , which is the total impedance of the solar cell module 11. FIG. 11A shows the dependence of the intensity of the impedance Z _PV of the solar cell module 11 on the frequency F, and FIG. 11B shows the dependence of the phase of the impedance Z _PV on the frequency F. FIG. 11 shows measurement at night when the solar cell module 11 does not generate power. As an example, the lower limit frequency is set to F ₁ = 1 kHz, the upper limit frequency is set to F ₂ = 4.8 MHz, and the frequency F is set to F ₁ to F _2. while increasing, the results of measuring the impedance Z _PV solar cell module 11.

Similar to the measurement result of FIG. 3, when the frequency is F = 0.68 MHz, the first resonance peak due to L _c of the output cable 14 and L _{s of the} module body and the junction capacitance C _d is seen. A new second resonance peak also appears near the frequency of F = 3 MHz. The second resonance peak, the output cables 14 and tabs wiring inductance L _{c +} L _s and parallel resonance due to the capacitance C _e between the metal frame 12, the inductance L _g and the wiring member and the metal frame 12 of the ground wire 23 of the This is thought to be due to series resonance due to the capacitance C _e between them.

As described in detail in the measurement results shown in FIG. 3, by calculating the total impedance of the equivalent circuit and footing the obtained impedance curve to the actual measurement value, circuit constants L _c , C _d , R _sh , L _s , R _s , and C _e can be obtained at a time. In the vicinity of the first resonance peak (F = 0.68 MHz) and the second resonance peak (F to 3 MHz), the impedance changes greatly, so when fitting is performed in the entire frequency region including these two regions, Circuit constants can be obtained with high accuracy. The actual fitting result is shown in FIG. 11, and it can be seen that the measured value and the fitting result are in good agreement.

  As described above, in the second embodiment, since there is no mechanical or electrical switch for switching the measurement in the diagnostic circuit, the long-term reliability of the diagnostic circuit of the solar cell module can be improved. Further, when the solar cell module 11 is diagnosed, the impedance measurement (S113) and the equivalent circuit analysis (S114) are each performed once, so that there is an advantage that the diagnosis time can be shortened.

In the diagnostic method of the measurement result shown in FIG. 7 of the first embodiment, the resonance peak can be moved to the low frequency side without limitation by increasing L _g of the inductor 24 for adjusting the resonance point. However, the diagnostic method of the second embodiment, when the value of L _g is increased, C _{e, L g,} the impedance of the branch circuit comprising R _g is increased, this circuit stops flowing current of the high frequency signal is almost End up. Therefore, an appropriate numerical range exists for the value of L _g of the inductor 24 for adjusting the resonance point. FIG. 12 is a diagram illustrating a result of obtaining the total impedance Z _PV of the solar cell module by simulation using the value of L _g as a parameter. Here, the circuit constants other than L _g was used the values obtained in the diagnostic. That is, L _c = 0.8 μH, C _d = 25.4 nF, R _sh = 12.1 kΩ, L _s = 1.3 μH, R _s = 1.5 Ω, C _e = 661 pF, R _g = 4.9 Ω, The value of L _g was changed in the range of 1 to 20 μH. Increasing the value of L _g from 1μH to 20MyuH, the frequency of the second resonance peak decreases significantly from 4MHz to the 1.4 MHz, it sees that has the amount of change in impedance is considerably reduced at the same time the resonance point. When the amount of change in impedance is small, the accuracy of curve fitting is greatly deteriorated. Therefore, in order to sufficiently ensure the amount of change impedance at the resonance point, as shown in FIG. 12, it is necessary to a value of L _g below 20MyuH. In order for the resonance point to appear in a low frequency region of 3 MHz or less, the value of L _g may be set to 3 μH or more, and as a result, the range of 3 μH <L _g <20 μH may be set.

  Using the diagnostic circuit and diagnostic method of the second embodiment, in addition to the deterioration of the solar cell and the resistance of the module electrode or wiring part, the state of the sealing material can also be detected. Can be diagnosed automatically.

Embodiment 3 FIG.
FIG. 13: is a schematic block diagram which shows typically the circuit for a diagnosis used for the diagnosis of the solar cell module concerning Embodiment 3. As shown in FIG. Hereinafter, a description will be given centering on differences from the first embodiment. In the third embodiment, a method for diagnosing a specific solar cell module in a solar cell string in which a plurality of solar cell modules 11a, 11b, and 11c are connected in series will be described. In the following description, the plurality of solar cell modules 11a, 11b, and 11c may be collectively referred to as the solar cell module 11. As in the first embodiment, the terminal of the positive terminal box 13a, which is one output terminal of the terminal box 13 of the solar cell module 11b to be measured, is measured by the impedance measuring instrument 16 via the output cable 14a and the connection box 15. Connected to the central conductor 18 of the coaxial cable 17 connected to the terminal, a blocking capacitor 21 a for DC cut is inserted in the middle of this path, that is, in the connection box 15.

  On the other hand, the terminal of the negative terminal box 13b, which is the other output terminal of the terminal box 13 of the solar cell module 11b, passes through the output cable 14b and the connection box 15, and passes through the outer conductor 19 of the coaxial cable 17 and the ground of the impedance measuring device 16. In this path, a blocking capacitor 21b for DC cut is inserted in the connection box 15 also in this path.

  The high-frequency signal for measurement supplied from the impedance measuring device 16 to the solar cell module 11b has a sufficiently high frequency, in other words, the capacitance of the capacitor is sufficiently large, so that it easily passes through the blocking capacitor 21a. The DC voltage and current generated in the solar cell module 11b are cut by the blocking capacitors 21a and 21b. As a result, failure of the impedance measuring instrument 16 due to overvoltage generated in the solar cell module 11b can be prevented. In addition, since the outer conductor 19 on the return side of the coaxial cable 17 and the metal frame 12b of the solar cell module 11b are also electrically disconnected by the blocking capacitor 21b, the casing of the impedance measuring device 16 is grounded to prevent electric shock. Can be prevented. The metal frame 12b of the solar cell module 11b can also be grounded via the ground wire 23.

  Further, as shown in FIG. 13, diodes 25a and 25b for preventing interference (hereinafter, collectively referred to as diodes 25) are connected to the connecting portions between adjacent solar cell modules 11a, 11b, and 11c in the string. Has been inserted. In the nighttime when the impedance is measured, the solar cell module 11 does not generate power, so no voltage is generated across the diode 25, and the diode 25 is turned off. Therefore, the high-frequency signal supplied from the measurement terminal of the impedance measuring device 16 to the specific solar cell module 11b cannot be propagated to the other solar cell modules 11a and 11c adjacent to the solar cell module 11b. As a result, it is possible to measure the impedance of only the solar cell module 11b to be measured. On the other hand, in the daytime when the solar cell module 11 is generating power, a voltage is generated at both ends of the diode 25, so that the diode 25 is turned on, and the solar cell modules 11a, 11b, and 11c in the string are all electrically connected. Connected. In addition, if the impedance measurement of the solar cell module 11b is performed in such a state, the influence other than the module to be measured, in particular, the influence of the solar cell module 11a and the solar cell module 11c on both sides is also affected, making measurement difficult. .

  As described above, in the third embodiment, since the interference preventing diode 25 is inserted between adjacent modules in a solar cell string in which a plurality of solar cell modules 11 are connected in series, impedance measurement is performed. During the nighttime when these are performed, these diodes 25 are turned off, and each module is electrically disconnected. Thereby, in the impedance measurement of the solar cell module 11, interference from other solar cell modules can be prevented. In addition, during the daytime power generation, the diode 25 is in an on state, and thus has no adverse effect on power transmission.

  In Embodiment 3, the connection box 15 is connected only to the solar cell module 11b to be measured. However, when the connection box 15 is connected in advance to the other solar cell modules 11a and 11c and measurement is performed. The impedance measuring device 16 and the connection box 15 may be connected. In this case, one interference preventing diode 25 may be prepared in each connection box, and one diode is inserted between adjacent solar cell modules.

  Deterioration of a specific solar cell in a solar cell string in which a plurality of solar cell modules are connected in series using the diagnostic circuit and diagnostic method of the third embodiment, module electrode or wiring section In addition to the poor resistance, the state of the sealing material can also be detected, and the solar cell module can be comprehensively diagnosed.

Embodiment 4 FIG.
Next, a diagnostic system for a solar cell module according to Embodiment 4 will be described. Below, it demonstrates centering on a different part from Embodiment 1 and 3. FIG.

  In the fourth embodiment, a solar cell module diagnosis system that constantly diagnoses individual solar cell modules constituting the solar power generation system will be described with reference to FIG. FIG. 14 is a schematic configuration diagram schematically illustrating a diagnostic system used for diagnosis of the solar cell module according to the fourth embodiment. In all the solar cell modules 11, the connection boxes 15a, 15b, 15c (hereinafter, collectively referred to as the connection box 15) and the impedance measuring instruments 16a, 16b, 16c (hereinafter, collectively referred to) described in the third embodiment. The impedance measuring device 16) is installed, and the output cable 14 of the solar cell module 11b is in series with the output cables 14 of the adjacent solar cell modules 11a and 11c via the connection box 15b as in the third embodiment. It is connected to the. In FIG. 14, the inside of the connection box 15 is not shown. An impedance measuring device 16 is directly connected to the connection box 15, and a host computer 27 as a control unit is connected to the impedance measuring device 16 via communication means 26 a, 26 b, 26 c (hereinafter collectively referred to as communication means 26). Connected. The impedance measuring device 16 transmits impedance information of the solar cell module 11 to the host computer 27 through the communication unit 26 and receives a measurement command from the host computer 27. The impedance measuring device 16 and the host computer 27 are provided with an interface for communicating with the communication means 26, and the host computer 27 also has means for communicating with the connection box 15. Furthermore, the impedance measuring device 16 may have means for communicating with the connection box 15. The host computer 27 can control ON / OFF of the first switch 22a and the second switch 22b of all the connection boxes 15 via the communication means 26. Here, it goes without saying that the communication means 26 does not necessarily have to be wired and may be wireless. In the fourth embodiment, the junction box 15 and the impedance measuring device 16 are separate casings, but they may be combined into a single casing. In the host computer 27, the equivalent circuit constant of each solar cell module 11 is extracted from the obtained frequency dependence data of impedance, and the presence or absence of deterioration of the solar cell module 11 or the degree of deterioration is detected by comparison with a reference value. To do.

  In the solar cell module diagnosis system as described above, the host computer 27 controls the impedance measuring device 16 and the connection box 15 via the communication means 26, so that the solar cell string or the entire solar cell module 11 of the solar power generation system is controlled. Impedance measurements can be performed sequentially. Impedance measurement is preferably in the nighttime when it is not exposed to sunlight, so use a clock built in the host computer 27, for example, automatically start measurement at each module with sunset, and investigate the occurrence of defects. Can do. When a defective solar cell module is detected, a solar power generation system is provided so that the amount of power generation during the day is not reduced by performing necessary maintenance such as replacement of the solar cell module 11 or repair of the output terminal box as soon as possible. Can be operated.

Embodiment 5. FIG.
Next, a diagnostic system for a solar cell module according to Embodiment 5 will be described. Below, it demonstrates centering on a different part from Embodiment 4. FIG.

In Embodiment 5, when always diagnosing the individual solar cell modules constituting the photovoltaic power generation system, temperature information is simultaneously acquired in addition to the impedance information of the solar cell module, and the solar cell module is obtained based on the temperature information. A more accurate diagnosis system that corrects the diagnosis result will be described. Although the equivalent circuit of the solar cell module has already been shown in FIG. 5, the values of the junction capacitance C _d , the parasitic capacitance C _e , the series resistance R _s, and the insulation resistance R _sh depend on the temperature of the solar cell module. Therefore, even if the solar cell module itself does not deteriorate, these values change if the temperature is different. Therefore, in order to detect the degradation state of the solar cell module with higher accuracy, it is necessary to acquire not only the impedance information of the solar cell module but also the temperature information at the same time, and appropriately correct the diagnosis result in consideration of the temperature difference. There is.

  FIG. 15: is a schematic block diagram which shows typically the circuit for a diagnosis used for the diagnosis of the solar cell module concerning Embodiment 5. As shown in FIG. In FIG. 15, a thermometer 28 as temperature measuring means is added to FIG. The thermometer 28 is connected to the host computer 27 via the communication means 29. In order to perform temperature correction in the diagnosis of the solar cell module 11, it is necessary to grasp the temperature of the solar cell module 11 when measuring the impedance of the solar cell module 11. However, as already explained, since the module diagnosis of the fifth embodiment is also usually performed at night, at the time of diagnosis, there is neither heat input by sunlight nor self-heating by power generation, and the temperature of the solar cell module 11 is almost equal to the temperature of the outside air. It can be considered that they match. Therefore, in Embodiment 5, the thermometer 28 which measures external temperature is installed in the diagnostic system instead of actually measuring the temperature of the solar cell module 11 of the solar power generation system. In addition, as long as the thermometer 28 can actually measure the temperature of the solar cell module 11, such a configuration may be used. In any case, the thermometer 28 can acquire temperature information that can be regarded as the temperature of the solar cell module 11. The thermometer 28 transmits the acquired temperature information to the host computer 27 through the communication means 29 and receives a measurement command from the host computer 27. The thermometer 28 includes an interface through which the temperature sensor unit communicates via the communication unit 29.

  In the solar cell module diagnosis system according to the fifth embodiment, the temperature correction is performed on the diagnosis result using the impedance information of each solar cell module 11 collected in the host computer 27 and the air temperature information as an index of the module temperature. Is possible. An example of module diagnosis with temperature correction will be described with reference to FIGS.

FIG. 16 is a diagram illustrating an example of a change with time of the insulation resistance R _sh of the equivalent circuit constant during the outdoor exposure period of the solar cell module, measured by the solar cell module diagnosis method according to the fifth embodiment. 16 (a) is a diagram showing a diagnosis result when temperature correction is not performed, and FIG. 16 (b) is a diagram showing a diagnosis result when temperature correction is performed. FIG. 16 shows the diagnostic results extracted during a relatively short exposure period of 6 months or less. FIG. 16A is a diagram illustrating a diagnosis result when the temperature correction described in the first embodiment and the second embodiment is not performed. Here, the method for measuring the impedance of the solar cell module 11 and the method for extracting the circuit constant from the frequency characteristic of the impedance are the same as those in the first and second embodiments, and the description thereof is omitted. In addition, the value of the insulation resistance R _{sh in} the figure is normalized by the initial value before outdoor exposure, and corresponds to the comparison result with the value when the solar cell module 11 is normal, and the solar cell. This is a value that quantitatively indicates the degree of deterioration of the insulating property of the module 11.

In this outdoor exposure test of the solar cell module, the exposure period is 189 days at the longest, that is, approximately 6 months, and the performance guarantee period of the solar cell module is more than 10 years. It is considered that no deterioration occurs in the battery module. Actually, the solar cell module after this exposure test was evaluated with a solar simulator, but no significant difference was observed in the power generation characteristics before and after the test. Thus, in such a short exposure test, the values of insulation resistance R _sh and other circuit constants should be nearly constant. However, as shown in FIG. 16 (a), when temperature correction is not performed, the value of the extracted R _sh varies considerably, and when the exposure period exceeds approximately 120 days, the value of R _sh is slightly increased. An increasing trend is seen. When the fluctuation amount of R _sh in the entire exposure period, that is, ± 3σ (σ: standard deviation) was calculated, it was found to be about ± 46%. Since the diagnostic result of R _sh , which is an index of module insulation, varies greatly in this way, even if the module insulation deteriorates and the value of R _sh decreases, the fluctuation amount is ± 46%. If it is within the range, it is difficult to detect the deterioration.

Next, a diagnosis result obtained by performing temperature correction for the diagnosis of the solar cell module will be described. As already shown in FIG. 15, the temperature of the place where the thermometer 28 is regarded as the temperature of the solar cell module 11 is constantly monitored by the thermometer 28. During the exposure test, the module temperature fluctuated from day to day and transitioned in the range of T _m = 17 ° C. to 47 ° C. Therefore, the relationship between the insulation resistance R _sh of the solar cell module in FIG. 16A and the module temperature T _m at the time of diagnosis was examined. The result is shown in FIG.

FIG. 17 is a diagram showing the correlation between the solar cell module equivalent circuit constant R _sh and the module temperature T _m measured by the solar cell module diagnosis method according to the fifth embodiment. As shown in FIG. 17, it was found that there is a strong negative correlation between the two. That is, the insulation resistance R _sh is large when the module temperature T _m is low, and conversely, the insulation resistance R _sh is small when the module temperature T _m is high. Were subjected to regression analysis on the data of the _{R sh} and _{T m,} between the _{R sh} and _{T m,} with a correlation coefficient r = _-0.925, the R sh = -0.0171T _m +1.74 I found that there was a relationship. That is, it was found that the temperature coefficient of the insulation resistance R _sh was α = −0.0171 ° C.− ¹ . When the regression line given by this linear expression, that is, R _sh = −0.0171 T _m +1.74 is superimposed on FIG. 17, most plots are shown in this temperature range from T _m = 17 ° C. to 47 ° C. You can see that it is on a straight line. Therefore, it is concluded that the reason why the extracted R _sh value fluctuated every day is mainly due to the difference in module temperature at the time of diagnosis.

As described above, it was found that the temperature of the solar cell module installed outdoors is not constant, and the extracted equivalent circuit constants fluctuate due to the difference in temperature when diagnosing the module. In addition, after installing a new or normal module outdoors, it can be expected that the module will not deteriorate at all in a relatively short period, for example, several months to one year. By examining the correlation between the circuit constants such as _d , C _e , R _s and R _sh and the module temperature T _m , the temperature coefficient of the circuit constant can be easily obtained. Thus, according to the temperature correction method of Embodiment 5, it is not necessary to measure and evaluate the temperature characteristics of the module in advance before installing the solar cell module, and data is collected for a certain period after installation. Just do it.

If the temperature coefficient of the circuit constant is known, the value of the circuit constant when the module temperature is T _m = 25 ° C., for example, can be estimated from the module temperature T _m at the time of diagnosis. By monitoring, it is considered that the influence due to the difference in module temperature at the time of diagnosis can be removed. In order to obtain the value of the circuit constant when the module temperature is T _m = 25 ° C., for example, in the case of the above-described insulation resistance R _sh , the temperature coefficient is α = −0.0171 ° C. ^−1. It can be determined from the relationship _sh (@ 25 ° C.) = R _sh (@T _m ) −α (T _m −25).

Actually, the change over time of R _sh (@ 25 ° C.) with temperature correction performed in this way is shown in FIG. 16 (b), and FIG. 16 (a) showing the result of diagnosis when temperature correction is not performed. In comparison, it can be seen that the fluctuation of R _sh (@ 25 ° C.) is greatly suppressed, and the fluctuation amount (± 3σ) in the entire exposure period is reduced to about ± 15%. Thus, since the random fluctuation amount of daily R _sh remains at about 15%, if the amount of change of R _sh caused by the deterioration of the module is 20% or more, this change can be captured. As already described, in the case where temperature correction is not performed, it cannot be considered that there is no change of at least 50%, so it can be said that the detection accuracy is greatly improved by the temperature correction method of the fifth embodiment.

In the fifth embodiment, the effect of the temperature correction has been described by taking the insulation resistance R _{sh of the} module as an example, but it corresponds to other circuit constants, that is, the series resistance R _{s of} the module, the junction capacitance C _{d of the} module, and the sealant. The same effect was obtained with respect to the parasitic capacitance C _e .

In the fifth embodiment, the air temperature in the vicinity of the solar cell module 11 is installed by the temperature gauge 28 measures, which was a module temperature T _m, paste the thermometer thermocouple on the surface of the solar cell module 11 with the T _m of a module temperature may be measured directly. That is, it is not necessary to measure or evaluate the temperature characteristic of the equivalent circuit constant of the module in advance, and the temperature coefficient can be obtained from the diagnosis result after installation.

  Further, the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the scope of the invention in the implementation stage. Further, the above embodiments include inventions at various stages, and various inventions can be extracted by appropriately combining a plurality of disclosed constituent requirements. For example, even if some constituent requirements are deleted from all the constituent requirements shown in the above embodiment, the problem described in the column of the problem to be solved by the invention can be solved, and is described in the column of the effect of the invention. In the case where a certain effect can be obtained, a configuration from which this configuration requirement is deleted can be extracted as an invention. Furthermore, the constituent elements over different embodiments may be appropriately combined.

  11, 11a, 11b, 11c Solar cell module, 12, 12a, 12b, 12c Metal frame, 13, 13a, 13b Terminal box, 14, 14a, 14b Output cable, 15, 15a, 15b, 15c Junction box, 16, 16a, 16b, 16c Impedance measuring device, 17 coaxial cable, 18 center conductor, 19 outer conductor, 20 dielectric, 21, 21a, 21b DC cut blocking capacitor, 22a first switch, 22b second switch, 23 ground Line, 24 Inductor for adjusting resonance point, 25, 25a, 25b Diode for preventing interference, 26, 26a, 26b, 26c, 29 Communication means, 27 Host computer, 28 Thermometer.

Claims (12)

Using a frequency variable impedance measuring instrument connected to a solar cell module having a conductive frame, the frequency characteristic of the impedance of the solar cell module is measured in a time zone when the solar cell included in the solar cell module does not generate power. A diagnostic method for diagnosing the solar cell module,
A frequency characteristic including a resonance point of impedance between the two output cables of the solar cell module, and a frequency characteristic including a resonance point of impedance between one of the two output cables and the frame; An analysis step of determining an equivalent circuit constant of the solar cell module from the measured frequency characteristics;
A determination step of comparing the equivalent circuit constant determined in the analysis step with an equivalent circuit constant acquired in advance to determine a change in the state of the solar cell module;
A method for diagnosing a solar cell module, comprising: The analysis step includes
Measuring a first frequency characteristic including a resonance point of impedance between two output cables of the solar cell module;
Determining an equivalent circuit constant for the first equivalent circuit based on the first frequency characteristic;
Measuring a second frequency characteristic including a resonance point of impedance between one of the two output cables and the frame;
Determining an equivalent circuit constant for a second equivalent circuit based on the second frequency characteristic;
The method for diagnosing a solar cell module according to claim 1, comprising: For the measurement of the frequency characteristic including the resonance point of the impedance between one of the two output cables and the frame, an inductor for adjusting the resonance point is inserted between the frame and the ground of the impedance measuring instrument. It performs using a circuit. The diagnostic method of the solar cell module of Claim 1 or 2 characterized by the above-mentioned. Using a frequency variable impedance measuring instrument connected to a solar cell module having a conductive frame, the frequency characteristic of the impedance of the solar cell module is measured in a time zone when the solar cell included in the solar cell module does not generate power. A diagnostic method for diagnosing the solar cell module,
Using a circuit in which an inductor for adjusting a resonance point is inserted between the frame and the ground of the impedance measuring device, a frequency characteristic including a resonance point of impedance between two output cables of the solar cell module is measured, An analysis step of determining an equivalent circuit constant of the solar cell module from the measured frequency characteristics;
A determination step of comparing the equivalent circuit constant determined in the analysis step with an equivalent circuit constant acquired in advance to determine a change in the state of the solar cell module;
A method for diagnosing a solar cell module, comprising: The solar cell module diagnosis method according to claim 4, wherein the resonance point adjusting inductor has a self-inductance of 3 μH to 20 μH. In the analysis step, using the relationship between the temperature dependence of the equivalent circuit constant estimated from the information of the equivalent circuit constant acquired in a certain period until the deterioration of the solar cell module and the temperature information of the solar cell module. The temperature correction of the equivalent circuit constant is performed. The method for diagnosing a solar cell module according to any one of claims 1 to 5.
Circuit means for connecting the first output terminal of the solar cell module having a conductive frame and the blocking capacitor;
Circuit means for connecting the blocking capacitor and a measurement terminal of the impedance measuring device;
Circuit means for connecting the second output terminal of the solar cell module and the first switch;
Circuit means for connecting the first switch to the ground of the impedance measuring device;
A resonance point adjustment circuit in which a resonance point adjustment inductor and a second switch are connected in series;
Circuit means for connecting the frame and one end of the resonance point adjusting circuit;
Circuit means for connecting the other end of the resonance point adjusting circuit and the ground of the impedance measuring device;
A diagnostic circuit for a solar cell module, comprising: The circuit for diagnosis of a solar cell module according to claim 7, wherein the self-inductance of the inductor for adjusting the resonance point is 3 µH or more and 20 µH or less. A first interference preventing diode;
Circuit means for connecting an output terminal of another solar cell module and the first interference preventing diode;
Circuit means for connecting the first output terminal and the first interference preventing diode;
The circuit for diagnosis of a solar cell module according to claim 7 or 8, further comprising: A second interference preventing diode;
Circuit means for connecting an output terminal of another solar cell module and the second interference preventing diode;
Circuit means for connecting the second output terminal and the second interference preventing diode;
The circuit for diagnosis of a solar cell module according to claim 9, further comprising: A diagnostic circuit for a solar cell module according to any one of claims 7 to 10,
The impedance measuring instrument;
A control unit for controlling the first switch and the second switch;
Communication means for transmitting impedance information of the solar cell module to the control unit, and transmitting control signals of the impedance measuring instrument, the first switch, and the second switch from the control unit;
A diagnostic system for a solar cell module comprising: The temperature measurement means which acquires the temperature information of the said solar cell module, and transmits to the said control part is further provided. The diagnostic system of the solar cell module of Claim 11 characterized by the above-mentioned.

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